Clinker crystal size

The subject of clinker grindability also has microscopical aspects and the most complete literature survey, to date, is that of Hills (1995) who enumerated most of the prevailing agreed-upon relations (such as decreasing alite crystal size increasing grindability). Other variables on which the interpretations were not as clear cut (such as percent liquid phase) were also listed. 

Tachihata, Kotani, andjyo (1981), in a laboratory study of the relationships between rate of heating, raw meal fineness, and other factors, concluded that clinkers with large crystal sizes in a narrow size range showed unfavorable grindability, and that cracks within the crystals and atthe boundaries were some of the most important factors in grindability. 

Scheubel (1988) found that the alite chord length could be used to construct a cumulative crystal size curve, the data from which were used to evaluate heating rates and retention times in various kiln systems. High-quality clinkers were said to have uniform granulometry, small silicate crystals, and easy grindability. 

The microscopy of two clinkers produced within 10 seconds by electron beam radiation at 1.2 MEV was described by Handoo and others (1992). Alite and belite appear well formed, with crystal sizes of 10 to 16 pm. Mortar strength at 28 days was said to be 470 kg/cm (46.1 MPa). 

A multiregressional equation predicting the 28-day mortar cube strength was presented by Rao, Akhouri, and Sinha (1992), the data coming from rotary and vertical shaft kiln clinkers. The prediction has a standard deviation of 17.9 kg/cm, utilizing alite and belite percentages and average crystal sizes. 

Detailed microscopical characteristics of clinkers from vertical shaft kilns, compared to laboratory burns, are presented by Ahluwalia and Raina (1992). Alite and belite crystal sizes in plant clinkers averaged approximately 21 and 19 pm, respectively, possibly accounting for high mortar strengths (44.8 MPa at 28 days). 

Overall increase in crystal size alite more than belite, which tends toward yellow color Lowering of feed to speed ratio, thinning clinker bed depth as burning zone moves uphill (Rader, 1985)... 

Dusty clinker (poor nodulization) and snowmen (a) Unfavorable temperature distribution (b) Too little melt (c) Too much coarse quartz, lime, slag (d) Heavy alkali circulation resulting in early crystal growth of belite and free lime and large silicate crystal size (Miller, 1980)... 

Photograph 7-11 Extremely heterogeneous clinker containing large concentrations of loosely packed yellow-amber belite and alite with a wide range of crystal sizes and, like the belite, a nonuniform distribution. Free lime is abundant (dark, round crystals). Sandy, silica-rich raw feed with coarse quartz. Gas-fired dry-process kiln, 3000 tons/day. (S A6631)... 

Crusts of belite on clinkers crystals of various sizes Semi-dry process, coal fuel with 15% to 20% ash, 0.5% to 1.5% sulfur (Hawthorne, Richey, and Demoulian, 1981)... 

Photograph 7-26 Experimental laboratory burn with raw mix containing quartz (44-75 pm) as a silica source. Average alite crystal size = 44 pm. 1000°C for 30 min, 1425°C for 10 min. Very rapid temperature change. Note abundant free lime inclusions in alite. Clinker courtesy of Joe Garcia, Capitol Cement, San Antonio, Texas. (S A6646)... 

Increasing C3A crystal size and number change in etch color Clinker drops out of kiln at successively lower temperature from maximum of 1500°C (Hawkins, 1979)... 

Total replacement of the raw feed silica with rice husk ash (Ghosh, Mohan, and Gandhi, 1992) resulted in more uniformity in the clinker silicate distribution, larger alite and smaller belite crystal sizes, and an approximately 11% higher 28-day strength (41.2 MPa), compared to a standard mix with 7% sand as the silica source. 

Zivanovic (1995) presented a description of clinkers made with silica fume, instead of quartz sand, as the primary silica component in the raw feed. The silica fume made up approximately 3.0 percent of the feed. Alite crystal size was reported to be from 50 to 200 pm and belite grains were said to be rounded and between 50 and 60 pm. No mention of belite nests was made. The cements made with silica fume or tuff and a particular marl, compared to other cements not made with these materials, did not require as much grinding and produced higher 28-day mortar strengths. 

Crystal size— mode, extreme range, and gradation (estimation of s as described above) unimodal or bimodal comparison witiiin and among clinkers. In order to establish a classification and nomenclature for clinker texture (that is, crystal size), the following scheme is proposed, based on the most commonly occurring alite crystal length ... 

Periclase Percentage crystal morphology average crystal size percentage larger than 15 microns association. Size and abundance distribution in and among clinkers. 

Ferrite Percentage crystal morphology association average crystal size color, size. Abundance variations within and among clinkers. 

Efch reactivity variations (specify etch and length of time). Crystal morphology crystal surface characteristics (depth of alteration) internal structure tendency for coarse cannibalism (masses greater than 5 times the average alite crystal size) inclusions. Size and abundance variations within and between clinkers. 

Etch reactivity variations crystal morphologies internal structure varieties (T)q)es "A," "B," or "C") inclusions percentages of nests and types of crystal packing and their percentages nest boundaries if nest crystals are different from others, describe separately. Crystal size, morphology, and abimdance variations within and among clinkers. 

Effects of common minor and trace elements derived from recycling waste materials in fuels and as raw materials for clinker production, as well as cement hydration, are summarized by Uchikawa and Hanehara (1997). Crystal size and optical property variations in clinker phases (alite, belite, aluminates, and ferrite), and their hydraulic reactivities, are shown to be related to concentrations of sulphm, magnesium, phosphorous, fluorine, chlorine, chromium, manganese, zinc, and many other elements. The cement industry is based in crystal chemistry. 

Akatsu, K., and Monna, I., "Effects of the Coarseness of Raw Materials on the Mineral Formation and Crystal Size of Portland Cement Clinker," Reviews,20th General Meeting, Cement Association of Japan, 1966, pp. 30-34. 

Butt, Y.M. Timashev, V.V. and Starke, "Phase Composition and Crystal Size of Quickly Fired Portland Cement Clinkers," Silikattechnik, Vol. 24,1973, pp. 10-12. 

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